It is important to map the termination of oil bearing formations as they near a salt dome. Such mapping is very difficult to accomplish using traditional surface seismic techniques. This is primarily because surface generated seismic energy reaching the vertical or near vertical surfaces of an active or passive salt dome or diapir can be reflected or scattered in directions other than back to the surface seismic detectors. Vertical Seismic Profiling surveys, or salt proximity surveys, in which seismic detectors are deployed in a wellbore and in which a seismic source is located on the surface can provide additional information, but not an adequate amount of information because of similar geometrical problems.
It is beneficial to deploy both a seismic energy source and one or more spaced apart seismic detectors in a single wellbore simultaneously. The seismic source/receiver system can be placed in a wellbore drilled near to the vertical or near vertical flank, but outside of, a salt dome. The seismic energy generated by the borehole deployed seismic source can travel along nearly horizontal paths and can be reflected or scattered back from the side or flank of the salt dome or diapir and from the steeply dipping earth formation beds near the flank of such a salt dome. The reflected seismic signals can then be detected from the spaced apart seismic detectors and recorded as a function of time.